Parallel scale-down tool to accelerate fermenterphile selection

Successful scale-up of fermentation processes relies on the selection of fermenterphiles, i.e. robust production strains that maintain optimal performance under industrial conditions [1]. Screening and selection of strains with fermenterphile
phenotype require suitable scale-down simulators that mimic relevant industrial conditions [2]. Commonly used scale-down simulators often have a large footprint and low throughput [3], hence they are used at later stages of bioprocess development, whereas including high-throughput scale-down systems at the early stages of bioprocess development would improve the chances of finding fermenterphiles [4]. In this study, we present a parallel scale-down tool based on the Sartorius Ambr® 250 high-throughput system to accelerate fermenterphile research in the early stage of bioprocess development. For the scale-down cultivation, we designed an intermittent feeding regime scale-down strategy to simulate the impact of substrate gradients in large bioreactors on Escherichia coli. In our design, intermittent feeding occurs in cycles of 1-2 minutes to impose repeated glucose starvation, however, the intermittent feeding regime can be adjusted freely to simulate a wide range of substrate gradients and liquid mixing times expected in industrialscale bioreactors. With the liquid handling solutions of Ambr® 250, metabolome and transcriptome analysis can be performed to elucidate the response of the strains to industrially relevant conditions. We postulate that the presented scale-down tool can be used to efficiently characterize the performance of microbial production strains in industrial fermentation processes and accelerate fermenterphile selection. This would allow the development of fermenterphile strains to be implemented at an early stage of bioprocess development.